Such a method is already known from practice in communication networks. In this process, a device sends a telegram and subsequently waits for a limited period of time for a response. If this response does not arrive, the device then switches into an energy-saving mode, which is characterized in that at least the HF radio is switched off because it consumes the most energy. However, a disadvantage in this process is that the device does not take other devices or already reserved bandwidths in the selected channel into consideration. Such a device sends unsynchronized and in doing so may interfere in its own network or foreign networks. As an alternative to this, it is known that the device, during high energy consumption, listens in a channel whether or not the base station would like to set up a communication. For this purpose, synchronization signals sent by the base station are necessary so that the device can recognize available communication partners. In this case it is advantageous that the device acts in a passive manner and in this way cannot interfere with any other device. However, a precondition for this is a fixed time reference between the received synchronization signal and the subsequent permitted registration request. In the case of very large time intervals between the synchronization signals, the device must switch the HF radio to listen for the entire time interval and in this process, it has high energy consumption. If a number of channels are available for selection, the same process must be carried out for said channels, which makes the energy balance even worse.